A variety of therapeutic modalities were attempted in AIDS patients. In an attempt to reconstitute the defective immune function of a single patient, we performed a bone marrow transplantation from a well heterosexual male to his homosexual twin brother with AIDS. In addition, we periodically transfused peripheral blood lymphocytes from the well to the AIDS twin. Partial reconstitution of immune function was achieved with transfer of delayed cutaneous hypersensitivity responses to the soluble antigen keyhole limpet hemocyanin (KLH), quantitive increase in the OKT4 subset of T cells, and an increase in blastogenic and cytotoxic lymphocyte function. Despite this, the reconstitution was only partial and had little impact on the clinical status of the patient. However, the study demonstrated the feasibility of using this approach as one of the therapeutic modalities in AIDS. A therapeutic trial of the administration of immune (gamma) interferon to AIDS patients was undertaken. This resulted in mild to modest improvement in the lesions of Kaposi's sarcoma and transient increases in certain in vitro immunological parameters. However, these changes were not impressive, nor were they of lasting duration. In general, patients continued to deteriorate clinically despite the modest improvements that were sometimes seen. Based on the demonstration in vitro that interleukin 2 (IL2) markedly enhanced and normalized the defective natural killer cell activity as well as the cell-mediated cytotoxicity against cytomegalovirus-infected targets of lymphocytes from AIDS patients, we are undertaking a trial of the administration of IL2 to patients with AIDS. In addition, we are currently examining the effects of repeated plasma exchange in AIDS patients. This study is based on the findings from other laboratories that AIDS patients have circulating inhibitors of immune function which may be compounding the underlying immunological defect. Future studies will be directed at combining several of the above-mentioned treatment modalities in an attempt to maximize our ability to reconstitute the defective immune function in AIDS.